Enclosed motor-compressor,particularly a small refrigerating machine

ABSTRACT

AN ENCAPSULATED REFRIGERATION MOTOR-COMPRESSOR HERMETICALLY SEALED IN A CAPSULE AND IN WHICH THE MOTOR IS COOLED BY A SEPARATE OIL FLOW THAN THAT LUBRICATING THE COMPRESSOR. THE TWO INDEPENDENT OIL FLOWS ARE TAKEN FROM A COMMON OIL PUMP BY A TWIN CENTRIFUGAL PUMP. THE MOTOR HAS A VERTICALLY DISPOSED HOLLOW MOTOR SHAFT TO WHICH IS ATTACHED A LENGTH OF TUBING IN COMMUNICATION WITH THE BORE OF THE SHAFT DEFINING A FIRST CENTRIFUGAL OIL PUMP. A SECOND LENGTH OF TUBING IS MOUNTED CIRCUMFERENTIALLY AND AXIALLY OF THE FIRST-MENTIONED LENGTH OF TUBING SPACED OUTWARDLY THEREFROM DEFINING A SECOND CENTRIFUGRAL OIL PUMP DRIVEN IN CONJUNCTION WITH THE FIRST PUMP FROM THE COMMON MOTOR SHAFT. A SINGLE CENTRIFUGRAL PUMP CONSISTING OF A SINGLE LENGTH OF TUBING CAN PROVIDE THE TWO OILS FLOWS BY CONSTRUCTING IT WITH AN AXIALLY EXTENDING ENLARGMENT AT THE ZONE OF DIVISION OF THE DISCHARGE INTO TWO OUTPUT FLOWS.

Feb. 2, 1971 v, VALBJORN ErAL 3,560,116

ENCLOSED MOTOR-COMPRESSOR, PARTICULARLY A SMALL I REFRIGERATING MACHINE Filed Jan. 30, 1969 Z& F

INVENTORS Knud V Valbjorn Hans U. Leffers Heinz MahncKe Bendi W Homer United States Patent 3,560,116 ENCLOSED MOTOR-COMPRESSOR, PAR- TICULARLY A SMALL REFRIGERAT- ING MACHINE Knud V. Valbjorn, Nordborg, Hans Ulrik Leffers and Heinz Mahncke, Sonderborg, and Bendt Wegge Romer, Augustenborg, Denmark, assignors to Danfoss A/ S, Nordborg, Denmark, 3 company of Denmark Filed Jan. 30, 1969, Ser. No. 795,267 Claims priority, application Germany, Feb. 1, 1968, P 16 28 157.5 Int. Cl. F04b 39/02 US. Cl. 417-372 9 Claims ABSTRACT OF THE DISCLOSURE An encapsulated refrigeration motor-compressor hermetically sealed in a capsule and in which the motor is cooled by a separate oil flow than that lubricating the compressor. The two independent oil flows are taken from a common oil sump by a twin centrifugal pump. The motor has a vertically disposed hollow motor shaft to which is attached a length of tubing in communication with the bore of the shaft defining a first centrifugal oil pump. A second length of tubing is mounted circumferentially and axially of the first-mentioned length of tubing spaced outwardly therefrom defining a second centrifugal oil pump driven in conjunction with the first pump from the common motor shaft. A single centrifugal pump consisting of a single length of tubing can provide the two oil flows by constructing it with an axially extending enlargement at the zone of division of the discharge into two output flows.

This invention relates generally to hermetic motorcompressors and more particularly to small encapsulated refrigeration machines.

Refrigeration compressors having a vertical crank shaft and a motor positioned below the compressor are known wherein a positive displacement pump at the lower end of the crankshaft delivers oil from the oil sump through an immersion tube and feeds it to various lubricating points such as shaft bearings, crank bearings and the compressor cylinder. The surplus oil is flung vertically upwardly against the inner wall surfaces of the unit capsule so that it is cooled thereon and runs along the wall of the capsule back into the oil sump at the lower end of the capsule. The motor rotor and stator are provided with dished receiving elements into which oil emerging from the lubricated parts can collect. The collected oil is applied to the motor for cooling the stator winding. However, this type of cooling has several deficiencies in that the quantity of oil delivered to the winding per unit time is very small because a considerable throttling effect occurs at the lubrication point passages. Furthermore, the oil has a very high temperature since it has picked up a considerable amount of heat lubricating the various parts, particularly oil lubricating the cylinder which is very hot. This heated oil is then used as a cooling medium and it is not as effective as it should be for cooling the motor and stator.

Furthermore, heretofore the refrigerant in a gaseous state within the capsule has had to effect part of the cooling and particularly parts of a motor-compressor such as the motor rotor and stator. This gas cooling is, however, dependent upon the particular conditions of operation and is often insufiicient at low evaporation temperatures.

It is a principal object of the invention to provide a motor-compressor unit having a refrigeration compressor lubricated with one flow of oil and other parts thereof ice cooled by a different oil flow and which would otherwise be endangered by fairly high temperatures developed.

Another object of the present invention is to provide a method of oil cooling independent of operating conditions in the external circuit of a refrigeration apparatus, thereby to reduce the great necessity of refrigerant gas cooling in the refrigeration compressor.

In the refrigeration compressor according to the invention, oil is delivered by a centrifugal pump as two streams independent of each other. One of the oil flows is for lubricating in the usual manner and the other stream cools motor parts directly.

By using an independent oil flow for cooling the rotor and stator coils, relatively cool oil unaffected by throttling effect, as in the prior art, is avoided. A very large quantity of oil is directly delivered to the motor rotor and stator and more particularly to their coil ends. The cooling oil reaches the oil ends at approximately the same temperature that exists in the oil sump since on way to the coil ends it undergoes no appreciable increase in temperature. Thus, the heat generated in the stator and motor winding which generally endangers the life of the motor is immediately dissipated without appreciable increase in the temperature of the oil in the sump since the oil flowing over the coil ends is only slightly heated because of its very large volume applied for cooling pur poses. Furthermore, since oil is continuously drawn from the oil sump and applied to the capsule cooling walls, the oil within the sump is generally kept at a rela tively reduced temperature.

In the unit according to the invention, the best cooling is effected by delivering a sufiicient quantity of cooling oil. In particular, the total quantity of oil circulated should be at least liters/H.P.-hour. The value of this quantity is greater than that of existing machines by approximately one order of magnitude.

In preferred embodiments of the invention, the invention is applied to motor-compressor units having a vertical motor shaft with the compressor disposed above the motor and the shaft having a bore through which oil flows axially and outwardly therefrom to various lubricating points. The shaft is provided with one or two centrifugal pumps for delivering oil to independent oil flows for lubrication and cooling of the apparatus.

In the embodiment in which one pump is used, it is constructed as a tube coaxial with the shaft and depending therefrom. The tube is provided with a conical lower end having an opening of lesser diameter than the diameter of the tube. A part of the axial length of the tube has an increased diameter and an opening for delivery of a stream of oil therefrom applied to passageways in the rotor for delivery to the stator with suitable deflecting means and cooling thereof. The remainder of the flow from the tube passes upwardly through the shaft bore and is applied through suitable passages to the parts to be lubricated.

In another embodiment, the centrifugal pump is constructed as two coaxial tubes with the inner tube depending from the shaft and the outer tube spaced outwardly therefrom defining a space between the two tubes. Both tubes are provided with a conical lower end portion so that upon rotation thereof in common with the water shaft oil flows through the inner tube upwardly through the shaft for lubrication and cooling oil flows between the two tubes and is delivered to a chamber defined between a lower short-circuiting ring and an upper end flange on the outer tube from where oil flows upwardly through axial passages in the rotor and onto the stator.

Preferably, the axial passageways formed in the stator are inclined from the vertical and in a direction opposite to the direction of rotation of the motor in order to improve the fiow of oil therethrough. The motor lower shortcircuiting ring or a deflector cooperative therewith in either embodiment is preferably provided with radial passages providing communication from the oil pump to the outer periphery of the rotor and delivery of oil to the lower ends of the stator which is axially longer than the rotor and is disposed circumferentially thereof.

Moreover, the axial bore of the shaft is in communication with upwardly extending axial passageways opening to the top of the shaft where a centrifuging disc is mounted that flings upwardly and outwardly the oil onto the inner wall of the capsule where cooling takes place as it works its way downwardly back to the sump at the lower end of the capsule. Preferably one of these passages is a direct passage without communication with other transverse passages providing lubricating oil. However, the upwardly extending passages in communication with lubricating passages apply excess oil to the centrifuging disc for cooling of the sulplur oil, as above described.

A deflector or receiving device is provided near the lower outer edge of the stator for gathering the oil flow of the discharged oil flowing over the stator and oil entering therein bathes the lower coil ends.

Other features and advantages of the motor-compressor and the oil pumps in accordance with the present invention will be better understood as described in the following specification and appended claims, in conjunction with the following drawings, in which:

FIG. 1 is a longitudinal section through a motor-compressor unit embodying the invention;

FIG. 2 is a cross-section view taken along section line AA in FIG. 1;

FIG. 3 is a cross-section view through a rotor of another embodiment of the invention; and

FIG. 4 is a fragmentary longitudinal section view of a modification of the invention illustrating a modified centrifugal pump for delivery of lubricating and cooling oil as two independent outputs.

As illustrated in the drawings, a motor-compressor unit according to the invention comprises a hermetic capsule 1 in which is resiliently suspended, by a suspension system not shown, a refrigeration machine constituting a compressor having a downwardly extending portion 2 which supports a stator 5 of an electric drive motor and defines a bearing 3 for a shaft 4 of the motor. Upward extensions 6 on the motor support 2 form noise-reducing or absorbing chambers 7 of the compressor and a cylinder having an axis perpendicular to the plane of the drawing. An insert member 8, inserted into a central space defined by the extensions 6, seals or closes off the noise-reducing chambers 7 and forms or defines a second bearing 9 for the motor shaft. A support plate 13 supports the shaft vertically and a centrifuging disc or slinger ring 14 fixed to the rotatably driven shaft by a bolt 15, as illustrated.

The shaft 4 carries on a crank a crank bearing 11 to which is connected a connecting rod of a compressor piston, not shown. The motor has a rotor 12 mounted on the shaft 4. This rotor is provided with an upper shortcircuiting ring 16 and a lower short-circuiting ring 17. The motor stator 5 has upper coil ends 18 extending axially upwardly of the rotor and lower coil ends 19 extending and projecting axially downwardly of the rotor.

The motor shaft 5 has an axial bore 20 into which a first length of tubing 21 is inserted axially. The tubing extends axially downwardly and provides communication between it and the bore of the shaft and a hollow conical element or lower end portion 22 rotationally driven with the shaft 4 to function as a centrifugal oil pump. A transverse opening or passage 23 extends from the shaft bore 20 for lubricating the bearing 3 and three parallel axial passages or bores of reduced diameter 24, 25 and 26 extend axially upwardly from the main axial bore and terminate within the centrifuging disc .14, as illustrated in the drawings. A branch passage 27 for lubricating the crank bearing 11 extends from the bore 24 and another branch lubricating passage 28 for applying lubricating oil to the upper bearing 9 is in communication with the bore 26. Surplus oil not entering the branch passages along with the oil from the through passage 25 passes upwardly to the inside of the centrifuging disc 14 and is flung onto the inner wall of the capsule 1 over which it flows back into an oil sump 42 and is cooled in so doing.

According to the invention, a second length of tubing 29 is mounted on the first length of tubing 21 outwardly thereof and spaced therefrom extending axially of the inner or first length of tubing. The outer tubing is provided with a number of circumferentially spaced axially extending depressions 30 which extend radially inwardly defining inwardly-extending projections parallel with the axis of the two tubes to function as spacing elements and mounting the second length of tubing onto the inner or first length of tubing 21.

This outer length of tubing is provided at the lower end thereof with a hollow conical element or lower end portion 31 which terminates in an opening disposed axially spaced upwardly of an opening of the hollow conical element 22. The second hollow conical element 31 functions as a second centrifugal pump to deliver oil upwardly by way of centrifugal action and delivers oil in the space formed between the two tubes.

The upper end of the tube 29 is bent over outwardly to form a flange 32 which closely contacts the lower shortcircuiting ring 17, except at circumferentially spaced points where it has radial depressions defining radial passages 33. Between the two tubes 21 and 29, the short-circuiting ring, 17, the rotor 12 and the shaft 4, there is formed a cavity 34 from which passages 35 extend upwardly through the rotor 12. These passages open at the top between the bearing 3 and the short-circuiting ring 16, but at a point displaced rearwardly relative tothe direction of rotation of the rotor. The rotor support 2 forms a receiving wall 36 which surrounds the stator upper coil ends 18 and which is provided at its lower end with radial orifices or passages 37 so that the cooling oil entering a space 38, defined by the stator and its support, can be discharged over the outer periphery of the stator. At the lower end of the stator is disposed a receiving and deflecting device 39 which receives the oil discharged through the outlets 37 and bathes the lower coil ends 19. The device 39 can be constructed, for example, as a ring of sheet metal which is clamped onto the stator 5 by means of individual, circumferentially spaced, inwardly extending, ribs. A cavity 40 in the insert 7 communicates with the space 38 by way of openings 41, so that oil emerging from the lubricated parts can likewise flow away back to the sump by way of the space 38.

-In operation, the hollow conical element 22 supplies sufficient oil from the sump 42 in the usual manner, so that the lubrication points of the bearings and cylinder are properly lubricated. Furthermore, the surplus oil passes upwards through the three axial bores 24-26 and into the dished plate 14 and is slung onto the wall of the capsule 1. The oil is subjected to extensive cooling during its flow along the wall of the casing back to the sump 42.

The second hollow conical element 31 delivers cooling oil through the chamber or space between the two coaxial tubes 21 and 29 into the annular chamber 34. The cooling oil passes upwards through the axial passages 35 and is flung by the short-circuiting ring 16 onto the stator upper coil ends 18. A second portion or flow of the cooling oil passes outwards through the radial passages 33 and is flung onto the stator lower coil ends 19. Some upwardly flung cooling oil flows downwards through the gap between the rotor and the stator; the greater volume, however, is received by the wall 36 and flows downwardly through the orifices 37 along the outer periphery of the stator 5 where it is received by the receiving device 39 and is additionally distributed over the stator lower coil ends 19. Since the resistance between the second pump and the upper end-face of the rotor axial passages 35 can be made very small, e.g., by selecting a sufficient number of correspondingly large passages, and since these pas sages 35 can themselves contribute to the flow of oil by their rearward inclination, large quantities of oil flow over the upper coil ends 18. Because of this, a considerable amount of heat is dissipated without the oil undergoing any great increase in temperature. If a positive-displacement pump, not shown, is used instead of those illustrated, such quantities of oil can be delivered over the coil ends even if the resistance to fiow is somewhat greater.

In an embodiment involving a /3 HP. machine having a stroke volume of 12 cm. the inner pump, i.e. the hollow conical element 22, delivered fifty-eight liters per hour, of which about 12 liters per hour were used for lubrication and about thirty-six liters per hour flwe dodwnthe and about thirty-six liters per hour flowed down the wall of the casing for return cooling. The outer pump, i.e. the hollow conical unit 31, on the other hand, delivers about eighty liters per hour, principally because of the greater effective diameter of the cone.

In the other embodiments illustrated in the drawings, similar reference numerals are used to designate parts similar to those already described. Thus, in another embodiment, fragmentarily illustrated in FIG. 3, grooves 43 are stamped out on the inner periphery of the rotor 12 and these are covered by the shaft 4. In this way, passages 44 are likewise created which can deliver the cooling oil to the upper coil ends.

FIG. 4 illustrates a single centrifugal pump, wherein the oil is divided into two streams at the level of the lower edge of the rotor. In order to accomplish this, a tube 45 comprising a lower hollow conical element 46 has a protuberance 47 at its upper end which bears against the short-circuiting ring 17. Opening 48 on the upper side of the protuberance 47 and circumferentially spaced thereon enable part of the oil from the pump to enter a chamber 49 and from there to pass into the passages 35 in the stator. Since additional drive or force results from the extension 47, the stream of oil branching off through the openings 48 is greater than the stream of oil rising through the shaft axial bore 20.

While preferred embodiments of the invention have been shown and described, it will be understood that many modifications and changes can be made within the true spirit and scope of the invention.

What we claim and desire to secure by \Letters Patent is:

1. In a motor-compressor unit, a motor having a vertically disposed motor shaft for driving the motor-compressor unit, a rotor connected to said shaft and a stator circumferentially of said rotor, pump means driven by said shaft delivering two independent flows of oil, one flow for lubricating said unit and another for cooling said rotor and stator without flowing cooling or lubricating other components of said unit, said pump means comprising two centrifugal oil pumps driven in common by said shaft, said two centrifugal oil pumps comprising two coaxial tubes defining a suction space therebetween, said tubes each having a conical lower end portion, said shaft having a bore, an inner one of said tubes being disposed. as an axial extension of said bore, and means outwardly of said shaft to guide oil flow from said space to said stator and rotor, said rotor comprising axial passages in communication with said space for flowing oil therethrough, said passages being disposed inclined in a direction away from the direction of rotation of said rotor, said rotor comprises a lower short-circuiting ring and an upper short-circuiting ring, and said passages ter- 2. In a motor-compressor unit according to claim 1, in

which each of said tubes comprises a conical lower end portion, each portion having an opening having a diameter less than the diameter of each respective tube.

3. In a motor-compressor unit according to claim 2, in which the outer one of said two coaxial tubes comprises an upper end outwardly extending flange engaging said lower short-circuiting ring defining an annular chamber jointly with said rotor, said short-circuiting ring and said shaft, said chamber communicating with said space, and said passages communicating with said chamber.

4. In a motor-compressor unit according to claim 3, in which said motor-compressor comprises a dished member connected to an upper end of said shaft, said shaft having oil passageways providing communication between the interior of said dished member and said bore, a capsule hermetically enclosing said motor-compressor, and said dished member being disposed relative to the interior of said capsule in position for flinging oil therefrom onto inner wall surfaces of said capsule for cooling thereon.

5. In a motor-compressor unit according to claim 3, in which said lower short-circuiting ring is disposed circumferentially of said chamber defining an outer periphery thereof, said lower short-circuiting ring and said flange defining radial passages providing communication between said chamber and the exterior of said lower short-circuiting ring.

6. In a motor-compressor unit according to claim 5, in which said rotor has greater axial length than said stator, whereby oil outflow from said passages cools the ends of said stator and said rotor.

7. In a motor-compressor unit according to claim 6, in which said motor-compressor comprises a downwardly extending support wall member outwardly of said rotor upper end, said support wall having openings spaced thereon in a circumferential direction for allowing oil to flow therethrough onto the outer periphery of said stator.

8. In a motor-compressor unit according to claim 7, including a dished receptor disposed under the lower end of said stator to receive oil flowing over the periphery of said stator for cooling said lower end of said stator.

9. In a motor-compressor unit according to claim 1, in which said pump means comprises a tube disposed as an extension of said shaft, said shaft having an axial bore in communication with said tube, said tube having an enlarged portion having an enlarged diameter along an axial length thereof, said enlarged portion having a plurality of openings spaced in a circumferential direction, said tube having a conical lower end converging in a direction inwardly of the tube, said conical lower end having an opening for taking an oil suction when said tube is driven rotationally by said shaft, and one of said oil flows flowing upwardly through said bore and said another flow flowing outwardly through said openings.

References Cited UNITED STATES PATENTS 1,967,033 7/1934 Lipman 230207X 2,504,528 4/1950 Hume 230-206 3,253,776 5/1966 Parker 230206 ROBERT M. WALKER, Primary Examiner 

